Divers working in 90 feet of water are searching frantically for about 300 people -- most of them high school students -- still missing in the wreckage of an overnight ferry that sank off South Korea's southern coast Wednesday with 459 people aboard.

At least four people are confirmed dead and 55 injured.

Ships, airplanes and helicopters buzzed around the side as the 450-foot long ferry listed and slowly sank 12 miles off the island of Byeongpoong. Rescuers pulled dazed students, many wearing life jackets,out of the water or off the vessel.

Lee Gyeong-og, a vice minister for South Korea's Public Administration and Security Ministry, said 30 crew members, 325 high school students, 15 school teachers and 89 non-student passengers were aboard the ship.

Kang Byung-kyu, a government minister, said the two dead are a female crew member and a male believed to be a student. A third body was found in the water but details were sketchy. A coast guard officer confirmed a fourth fatality but had no immediate details about it.

Kang Byung-kyu said 164 people were rescued, of whom 55 were injured. He said 292 people were missing, likely either trapped inside the ship or floating in the ocean.

Even after the ferry went down, divers continue to search for survivors who may have found pockets of air in the submerged wreckage. A U.S. Navy ship was joining the rescue effort.

One student, Lim Hyung-min, told broadcaster YTN after being rescued that he and other students jumped into the ocean wearing life jackets and then swam to a nearby rescue boat.

"As the ferry was shaking and tilting, we all tripped and bumped into each another," Lim said, adding that some people were bleeding. Once he jumped, the ocean "was so cold. ... I was hurrying, thinking that I wanted to live."

The Yonhap news agency, quoting government officials, says the 6,325-ton Sewol was carrying 459 people, including 325 students from a high school in Ansan, just south of Seoul, when it sent out a distress signal at 8:58 a.m.

Several survivors reported hearing a "loud impact" before the ship started listing and turning on its side, Reuters reports. Officials said it was not immediately clear what caused the vessel to sink.

The overnight ferry from Inchon was 11 hours into a 14-hour trip to the tourist island of Jeju. The ferry, built in 1994, makes the trip twice a week, the Yonhap news agency reports.